The present invention relates to an integrally anchored fiber-reinforced concrete overlay and to a method of making the same.
A commonly used procedure for restoring the original riding quality of highway and airfield pavements is to overlay the existing deteriorated roadway with a new layer of construction material such as asphaltic concrete or Portland cement concrete. Typically, the overlay procedure involves extensive preparation of the existing pavement in the form of removal of deteriorated pavement material, scarification of the existing wearing surface, and application of a bonding layer to tie the new overlay firmly into the existing pavement. The conduct of these steps is both time consuming and costly.
Even when the old pavement has been properly prepared, it is not uncommon for the bond between the new overlay and the old pavement to exhibit disruption. This event frequently is followed by the onset of cracking and spalling distress in the overlay material. The problems in bonding of overlay materials to existing pavements has limited the use of this pavement restoration option.
There are situations in which, because of the severity of traffic conditions, overlays cannot be considered since it is very certain that they will not function satisfactorily for a sufficient period of time. The only acceptable alternative in many of these cases is to fully excavate the old pavement and completely replace it with a new pavement.
The most commonly used overlay material for restoring deteriorated highway pavements is asphaltic concrete. It is generally recognized that while the material can be conveniently and expeditiously placed, its performance record leaves much to be desired. Additionally, because of the great weight of modern-day aircraft, asphaltic concrete is typically not the material of choice for the overlay of airfield pavements. Thus, in the restoration of airfield pavements, restoration alternatives frequently come down to complete replacement or the use of relatively thick sections of conventional Portland cement concrete.
In addition to the overlay restoration of existing, deteriorated pavements, there are other construction situations in which a fully bonded overlay or surfacing material could be a cost-effective restoration procedure. Examples include hydraulic structure applications (stilling basins, fliplips, spillways), open culverts, bridge decks, and industrial floors.
U.S. Pat. No. 4,339,289, entitled Concrete Overlay Construction, issued July 13, 1982 to the inventor of the present invention and incorporated herein by reference, describes a fiber-reinforced overlay incorporating 4 to 12% by volume steel fibers. However, in the preparation of the overlay, the overlay material is bonded to the substrate paving material through the use of bonding agents such as a Portland cement slurry or an epoxy adhesive. These bonding agent materials have been, and are, currently used in an effort to provide a durable bond between overlay materials and pavements. Not infrequently, despite the use of these bonding agents, disruption does occur between the overlay material (whatever its composition) and the substrate pavement.
Thus, an overlay and surfacing material is needed having good resistance to cracking, spalling, wear, and other forms of distress and which remains fully bonded to the substrate on which it has been placed. The integrally anchored steel fiber-reinforced concrete overlay and surfacing material of the present invention meets these qualifications, the combination of which is not currently available in a single-materials system.